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MicroRNA-1 (miR-1) is approved involved in cardiac hypertrophy, but the underlying molecular mechanisms of miR-1 in cardiac hypertrophy are not well elucidated. The present study aimed to investigate the potential role of miR-1 in modulating CDKs-Rb pathway during cardiomyocyte hypertrophy. A rat model of hypertrophy was established with abdominal aortic constriction, and a cell model of hypertrophy was also achieved based on PE-promoted neonatal rat ventricular cardiomyocytes (NRVCs). We demonstrated that miR-1 expression was markedly decreased in hypertrophic myocardium and hypertrophic cardiomyocytes. Dual luciferase reporter assays revealed that miR-1 interacted with the 3'UTR of CDK6, and miR-1 was verified to inhibit CDK6 expression at the posttranscriptional level. CDK6 protein expression was observed increased in hypertrophic myocardium and hypertrophic cardiomyocytes. Morover, miR-1 mimic, in parallel to CDK6 siRNA, could inhibit PE-induced hypertrophy of NRVCs, with decreases in cell size, newly transcribed RNA, expressions of ANF and β-MHC, and the phosphorylated pRb. Taken together, our results reveal that derepression of CDK6 and activation of Rb pathway contributes to the effect of attenuation of miR-1 on provoking cardiomyocyte hypertrophy.

Objective: Evidence shows that both macrophage migration inhibitory factor (MIF) and GLUT4 glucose transporter are involved in diabetic cardiomyopathy (DCM), but it remains largely unknown whether and how MIF regulates GLUT4 expression in cardiomyocytes. The present study aims to investigate the mechanism underlying the modulation of GLUT4 by MIF in cardiomyocytes., Material and Methods: Activations of AKT and AMPK signaling, and expressions of MIF, GLUT4 and the candidate GLUT4 regulation associated transcription factors in the diabetic mouse myocardium were determined. The screened transcription factors mediating MIF-promoted GLUT4 expression were verified by RNA interference (RNAi) and electrophoretic mobility shift assay (EMSA), respectively., Results: MIF was increased, but GLUT4 was decreased in the diabetic mouse myocardium. MIF could enhance glucose uptake and up-regulate GLUT4 expression in NMVCs. Expressions of transcription factor MEF2A, -2C, -2D and Zac1 were significantly up-regulated in MIF-treated neonatal mouse ventricular cardiomyocytes (NMVCs), and markedly reduced in the diabetic myocardium. Knockdown of MEF2A, -2C, -2D and Zac1 could significantly inhibit glucose uptake and GLUT4 expression in cardiomyocytes. Moreover, EMSA results revealed that transcriptional activities of MEF2 and Zac1 were significantly increased in MIF-treated NMVCs. AMPK signaling was activated in MIF-stimulated NMVCs, and AMPK activator AICAR could enhance MEF2A, -2C, -2D, Zac1 and GLUT4 expression. Additionally, MIF effects were inhibited by an AMPK inhibitor compound C and siRNA targeting MIF receptor CD74, suggesting the involvement of CD74-dependent AMPK activation., Conclusions: Transcription factor MEF2 and Zac1 mediate MIF-induced GLUT4 expression through CD74-dependent AMPK activation in cardiomyocytes., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: To investigate the association of desmoplakin with the distribution and function of Nav1.5 by RNA silencing technology in HL-1 cells., Methods: HL-1 cells with desmoplakin expression suppression by RNA silencing were examined for desmoplakin and Nav1.5 protein expressions by Western blotting, and the distribution and co-location of desmoplakin and Nav1.5 protein were detected by immunofluorescence staining. Patch-clamp recording was applied to analyze the changes in whole-cell sodium current after desmoplakin silencing., Results: Compared with the untreated group and negative control group, the cells with desmoplakin silencing showed obviously reduced expressions of desmoplakin and Nav1.5 proteins. Co-localization of desmoplakin and Nav1.5 was detected at cell-cell contact in untreated and control conditions, and desmoplakin expression silencing induced a drastic redistribution of Nav1.5 with decreased peak current density (156.3∓6.2 vs 41.8∓3.1, n=6, P<0.05), a shift in voltage dependence of steady-state inactivation (-42 mV vs -61 mV, n=5, P<0.05), and prolonged time of recovery from inactivation., Conclusion: Desmoplakin silencing caused redistribution of Nav1.5 protein and also changes in its electrophysiological properties in HL-1 cells.

Aim of This Study: The panax notoginseng saponins (PNS) have been clinically used for the treatment of cardiovascular diseases and stroke in China. Evidences demonstrated that PNS could protect cardiomyocytes from injury induced by ischemia, but the underlying molecular mechanisms of this protective effect are still unclear. This study was aimed to investigate the protective effect and potential molecular mechanisms of PNS on apoptosis in H9c2 cells in vitro and rat myocardial ischemia injury model in vivo., Materials and Methods: H9c2 cells subjected to serum, glucose and oxygen deprivation (SGOD) were used as in vitro models and SD rats subjected to left anterior descending (LAD) coronary artery ligation were used as in vivo models. The anti-apoptotic effect of PNS was evaluated by Annexin V/PI analysis or TUNEL assay. Mitochondrial membrane potential (Δψm) was detected by JC-1 analysis. The expression of Akt and phosphorylated Akt (p-Akt) were detected by western blot assay., Results: PNS exhibited anti-apoptotic effect both in H9c2 cells and in ischemic myocardial tissues. However, the effect was blocked in vitro by LY294002, a specific PI3K inhibitor. The anti-apoptotic effect of PNS was mediated by stabilizing Δψm in H9c2 cells. Furthermore the indices of the left ventricular ejection fractions (EF), left ventricular fractional shortening (FS), left ventricular dimensions at end diastole (LVDd) and left ventricular dimensions at end systole (LVDs) suggested that PNS improved rats cardiac function. PNS significantly increased p-Akt both in H9c2 cells and in ischemic myocardial tissues and this effect was also blocked by LY294002 in H9c2 cells., Conclusion: Results of this study suggested that PNS could protect myocardial cells from apoptosis induced by ischemia in both the in vitro and in vivo models through activating PI3K/Akt signaling pathway., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)